scholarly journals Different spectroscopic behavior of coupled and freestanding monolayer graphene deposited by CVD on Cu foil

2018 ◽  
Vol 458 ◽  
pp. 580-585 ◽  
Author(s):  
Oreste De Luca ◽  
Rossella Grillo ◽  
Marco Castriota ◽  
Alfonso Policicchio ◽  
Maria Penelope De Santo ◽  
...  
Keyword(s):  
Monolayer Graphene ◽  
Cu Foil ◽  
Spectroscopic Behavior

NO2 gas sensing properties of bilayer graphene by CVD method

Sensor Review ◽  
2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hui Li ◽  
Zengwen Zhang ◽  
Ruiyang Fang ◽  
Zhihui Gao ◽  
Wei He
Keyword(s):  
Recovery Time ◽  
Gas Sensing ◽  
Uv Light ◽  
Bilayer Graphene ◽  
Monolayer Graphene ◽  
Content Type ◽  
Desorption Time ◽  
The Difference ◽  
Cu Foil ◽  
Difference Effect

Purpose The authors designed those experiments to test the sensitivity of graphene when it is exposed to NO2 gas, to find a way to decrease the recovery time of graphene and to find the difference effect between monolayer and bilayer graphene in the experiments. Design/methodology/approach The authors transferred graphene from film on Cu foil to NO2 sensor sample and measured the resistances of on monolayer and bilayer graphene when they were exposed to NO2 gas under different concentration; then, the authors obtained the results. Findings The results show that monolayer graphene exhibits a linear response when the NO2 concentration is below 20 ppm. But the monolayer graphene will not be so sensitive to NO2 gas when the concentration continues to reduce. The desorption time of monolayer graphene is longer when compared with bilayer graphene. It shows faster recovery time and higher response of bilayer graphene under low NO2 concentration. And the limit detectable NO2 concentration of bilayer graphene is 50 ppb. Desorption time of bilayer graphene is shortened to below 20 s under UV light. Originality/value The authors found a reliable way to decrease the recovery time of graphene when it is exposed NO2 gas and got the concrete data.

scholarly journals Nitrogen cluster doping for high-mobility/conductivity graphene films with millimeter-sized domains

2019 ◽  
Vol 5 (8) ◽  
pp. eaaw8337 ◽  
Author(s):  
Li Lin ◽  
Jiayu Li ◽  
Qinghong Yuan ◽  
Qiucheng Li ◽  
Jincan Zhang ◽  
...  
Keyword(s):  
Carrier Mobility ◽  
Hexagonal Lattice ◽  
High Mobility ◽  
Monolayer Graphene ◽  
Carrier Scattering ◽  
Scattering Centers ◽  
N Doping ◽  
Doped Graphene ◽  
Device Applications ◽  
Cu Foil

Directly incorporating heteroatoms into the hexagonal lattice of graphene during growth has been widely used to tune its electrical properties with superior doping stability, uniformity, and scalability. However the introduction of scattering centers limits this technique because of reduced carrier mobilities and conductivities of the resulting material. Here, we demonstrate a rapid growth of graphitic nitrogen cluster–doped monolayer graphene single crystals on Cu foil with remarkable carrier mobility of 13,000 cm2 V−1 s−1 and a greatly reduced sheet resistance of only 130 ohms square−1. The exceedingly large carrier mobility with high n-doping level was realized by (i) incorporation of nitrogen-terminated carbon clusters to suppress the carrier scattering and (ii) elimination of all defective pyridinic nitrogen centers by oxygen etching. Our study opens up an avenue for the growth of high-mobility/conductivity doped graphene with tunable work functions for scalable graphene-based electronic and device applications.

Structural and Optical Properties of GaN Film on Copper and Graphene/Copper Metal Foils Grown by Laser Molecular Beam Epitaxy

2020 ◽  
Vol 20 (6) ◽  
pp. 3929-3934 ◽  
Author(s):  
C. Ramesh ◽  
P. Tyagi ◽  
S. Bera ◽  
S. Gautam ◽  
Kiran M. Subhedar ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Monolayer Graphene ◽  
Near Band Edge ◽  
Band Edge Emission ◽  
Laser Molecular Beam Epitaxy ◽  
Metal Foils ◽  
Direct Growth ◽  
Cu Foil ◽  
Gan Film

We report the direct growth of crystalline GaN on bare copper (Cu) and monolayer-graphene/Cu metal foils using laser molecular beam epitaxy technique at growth temperature of 700 °C. The surface morphology investigated with field emission scanning electron microscopy revealed that the size of GaN grains for film grown on bare Cu falls in range of 90 to 160 nm whereas large grains with size of ˜200 to 600 nm was obtained for GaN grown on graphene/Cu foil under similar growth condition. The transverse optical mode of cubic GaN and E2 (high) phonon mode for wurtzite GaN phases were obtained on the GaN film grown on Cu and graphene/Cu metal foils as deduced by Raman spectroscopy. The photoluminescence (PL) spectroscopy studies showed that the near band edge emission peaks for GaN on Cu and graphene/Cu consist two major peaks at 3.26 and 3.4 eV, corresponding to cubic and wurtzite GaN, respectively. The Raman and PL studies disclosed that the mixed phase growth of GaN occurs on these foils and better structural and optical quality for GaN on graphene/Cu foil. The direct growth of GaN on two dimensional graphene on polycrystalline metal foils is beneficial various transferrable and flexible opto-electronics device applications.

scholarly journals Nano-Physical Characterization of Chemical Vapor Deposition-Grown Monolayer Graphene for High Performance Electrode: Raman, Surface-Enhanced Raman Spectroscopy, and Electrostatic Force Microscopy Studies

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2839
Author(s):  
Won-Hwa Park
Keyword(s):  
Raman Spectroscopy ◽  
Carrier Mobility ◽  
Electrostatic Force ◽  
Chemical Vapor ◽  
Surface Enhanced Raman Spectroscopy ◽  
Monolayer Graphene ◽  
Force Microscopy ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Cu Foil

To achieve high-quality chemical vapor deposition of monolayer graphene electrodes (CVD-MG), appropriate characterization at each fabrication step is essential. In this article, (1) Raman spectroscopy/microscopy are employed to unravel the contact effect between the CVD-MG and Cu foil in suspended/supported formation. (2) The Surface-Enhanced Raman spectroscopy (SERS) system is described, unveiling the presence of a z-directional radial breathing-like mode (RBLM) around 150 cm−1, which matches the Raman shift of the radial breathing mode (RBM) from single-walled carbon nanotubes (SWCNTs) around 150 cm−1. This result indicates the CVD-MG located between the Au NPs and Au film is not flat but comprises heterogeneous protrusions of some domains along the z-axis. Consequently, the degree of carrier mobility can be influenced, as the protruding domains result in lower carrier mobility due to flexural phonon–electron scattering. A strongly enhanced G-peak domain, ascribed to the presence of scrolled graphene nanoribbons (sGNRs), was observed, and there remains the possibility for the fabrication of sGNRs as sources of open bandgap devices. (3) Electrostatic force microscopy (EFM) is used for the measurement of surface charge distribution of graphene at the nanoscale and is crucial in substantiating the electrical performance of CVD-MG, which was influenced by the surface structure of the Cu foil. The ripple (RP) structures were determined using EFM correlated with Raman spectroscopy, exhibiting a higher tapping amplitude which was observed with structurally stable and hydrophobic RPs with a threading type than surrounding RPs. (4) To reduce the RP density and height, a plausible fabrication could be developed that controls the electrical properties of the CVD-MG by tuning the cooling rate.

scholarly journals Strong localization in suspended monolayer graphene by intervalley scattering

2021 ◽  
Vol 103 (8) ◽  
Author(s):  
Cenk Yanik ◽  
Vahid Sazgari ◽  
Abdulkadir Canatar ◽  
Yaser Vaheb ◽  
İsmet İ. Kaya
Keyword(s):  
Monolayer Graphene ◽  
Strong Localization ◽  
Intervalley Scattering

Electronic phase derived impedance spectroscopic behavior of La0.5Nd0.2A0.3MnO3 manganites

2021 ◽  
pp. 160930
Author(s):  
V.S. Vadgama ◽  
Keval Gadani ◽  
Bhagyashree Udeshi ◽  
Manan Gal ◽  
K.N. Rathod ◽  
...  
Keyword(s):  
Electronic Phase ◽  
Spectroscopic Behavior

scholarly journals Critical View on Buffer Layer Formation and Monolayer Graphene Properties in High-Temperature Sublimation

2021 ◽  
Vol 11 (4) ◽  
pp. 1891
Author(s):  
Vallery Stanishev ◽  
Nerijus Armakavicius ◽  
Chamseddine Bouhafs ◽  
Camilla Coletti ◽  
Philipp Kühne ◽  
...  
Keyword(s):  
High Temperature ◽  
Charge Carrier ◽  
Buffer Layer ◽  
Free Charge Carrier ◽  
Monolayer Graphene ◽  
Free Charge ◽  
Layer Formation ◽  
Free Hole ◽  
Sublimation Growth ◽  
Insulating Substrates

In this work we have critically reviewed the processes in high-temperature sublimation growth of graphene in Ar atmosphere using closed graphite crucible. Special focus is put on buffer layer formation and free charge carrier properties of monolayer graphene and quasi-freestanding monolayer graphene on 4H–SiC. We show that by introducing Ar at higher temperatures, TAr, one can shift the formation of the buffer layer to higher temperatures for both n-type and semi-insulating substrates. A scenario explaining the observed suppressed formation of buffer layer at higher TAr is proposed and discussed. Increased TAr is also shown to reduce the sp3 hybridization content and defect densities in the buffer layer on n-type conductive substrates. Growth on semi-insulating substrates results in ordered buffer layer with significantly improved structural properties, for which TAr plays only a minor role. The free charge density and mobility parameters of monolayer graphene and quasi-freestanding monolayer graphene with different TAr and different environmental treatment conditions are determined by contactless terahertz optical Hall effect. An efficient annealing of donors on and near the SiC surface is suggested to take place for intrinsic monolayer graphene grown at 2000 ∘C, and which is found to be independent of TAr. Higher TAr leads to higher free charge carrier mobility parameters in both intrinsically n-type and ambient p-type doped monolayer graphene. TAr is also found to have a profound effect on the free hole parameters of quasi-freestanding monolayer graphene. These findings are discussed in view of interface and buffer layer properties in order to construct a comprehensive picture of high-temperature sublimation growth and provide guidance for growth parameters optimization depending on the targeted graphene application.

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